我有以下代码

func getAudioUrl(book: Book) -> URL? {
    guard let documentsDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first else {
        print("Unable to access documents directory")
        return nil
    }
    let fileUrl = documentsDirectory.appendingPathComponent("test-audio-" + String(book.id) + ".mp3")
    
    guard FileManager.default.fileExists(atPath: fileUrl.path) else {
        print("File does not exist")
        return nil
    }
    return fileUrl
}

  let fileURL = OfflineHandler.sharedInstance.getAudioUrl(book: currentItem as! Book)
  if (fileURL != nil) {
      let asset = AVAsset(url: fileURL!)
      avPlayerItem = AVPlayerItem(asset: asset)
  }
  
  NotificationCenter.default.addObserver(self, selector:#selector(self.itemDidFinishPlaying(_:)), name:NSNotification.Name.AVPlayerItemDidPlayToEndTime, object: avPlayerItem)
                
   audioPlayer = AVPlayer(playerItem: avPlayerItem)
   audioPlayer?.volume = 1.0
   audioPlayer?.automaticallyWaitsToMinimizeStalling = false
                
   updateCC()
   isReadyToPlay = true
                
   audioPlayer?.currentItem?.addObserver(self, forKeyPath: "status", options: ([.new, .initial]), context: nil)
    }

当用户没有Internet连接时，我正在尝试播放存储在“文档”文件夹中的音频文件。我得到一个错误，其中“status = unknown”（override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {）
有人知道我哪里做错了吗？